This invention relates to an electrical terminal apparatus, and particularly to a modular terminal block assembly enabling a number of individual terminal block modules to be stacked together for power distribution.
For industrial equipment, and particularly resistance welding machines, a large number of high power conductors are connected to power sources within power distribution panels. Frequently, there is a need to provided electrical connections for a number of machines from a single distribution panel. When dealing with high voltage sources, such as 440 VAC, which is often used for resistance welding equipment, the terminals must be well insulated from each other and physically separated to prevent inadvertent contact between adjacent electrical terminals. Along with this requirement for electrical isolation is the need to make the terminal assembly compact for efficient packaging and placement in the crowded environment of the distribution panel.
Instances of mechanical and/or electrical failure of the terminal assemblies necessitate their replacement along with the electrical insulators which separate individual terminals. Accordingly, there is a need for a terminal assembly which facilitates maintenance and repair.
Various designs for high-power terminal assemblies are presently known. The devices which have been in use for many years consist of a plate to which electrical terminals and insulating barrier plates are mounted. Although these devices operate satisfactorily, they suffer the disadvantages in that they are relatively bulky, and provide a fixed number of terminal slots which may not be consistent with the requirements of a particular application.
In an improved design manufactured and sold by the assignee of this application, a modular design terminal assembly (hereinafter called the prior art modular assembly) is provided having a multiplicity of terminal blocks which can be stacked to provide as many individual terminals as necessary. This prior art design provides the advantage of compactness and can be readily adapted for the desired number of electrical connections. Each terminal block provides a mounting point for the electrical terminals, and forms an insulating plate which acts as an insulating barrier between adjacent terminals. The individual terminal blocks of the prior art modular assembly are held together in a stacked configuration by threaded rods which compress the blocks together.
Replacement of a failed terminal or terminal block of the prior art design requires that the entire assembly must be removed from the distribution panel so that the threaded rods can be removed from the assembly to enable an individual terminal and terminal block to be removed. Such replacement requires a significant amount of time and labor, and constitutes wasted down-time for the associated equipment. Accordingly, it is desirable to provide an improved modular type terminal assembly which facilitates replacement of individual terminals and terminal blocks within the assembly.
The upper surface of the insulating plates of the prior art modular terminal assembly described above is covered by dead front safety covers which partially enclose the conductors and terminals. The dead front safety cover also provides a surface where identification labels for the circuits can be provided as an aid in diagnostics and servicing. With present modular terminal block assemblies, a number of individual safety covers is provided, each of which engages several of the insulator plates. When a complete terminal block assembly is disassembled, the separate plates must be removed. When the plates are removed they can be easily mixed up and incorrectly replaced on the device, or lost or damaged. Accordingly, there is a need to provide a safety cover assembly for a modular terminal block which can be mounted and dismounted as a unit.
The improved modular terminal assembly achieves the above mentioned desirable features. The present device is similar to the prior art modular device described above with a number of important design refinements. The holes through the terminal blocks are slotted to allow the block to be placed on the threaded rods between adjacent terminal blocks, thereby avoiding the necessity of axially loading each block on the rod. Accordingly, this design enables replacement of individual terminal blocks without complete disassembly of the entire unit. Moreover, the present device features an improved safety cover assembly having multiple pieces which can be snapped together, thus enabling it to be removed and replaced as a unit.
Additional benefits and advantages of the present invention will become apparent to those skilled in the art to which this invention relates from the subsequent description of the preferred embodiments and the appended claims, taken in conjunction with the accompanying drawings.